Nucleated RBCs can be located in

Options

A. Rat
B. Cat
C. Frog
D. Rabbit

Answer

To determine where nucleated red blood cells (RBCs) can be found, we need to analyze the characteristics of RBCs in different species.

### Step-by-Step Solution:

1. **Understanding RBCs**: Red blood cells (RBCs) are responsible for transporting oxygen throughout the body. In mammals, mature RBCs typically lack a nucleus, which allows for more space to carry hemoglobin, the protein that binds oxygen.

2. **Identifying the Species**: The question provides four options: rat, cat, frog, and rabbit. We need to examine the RBC characteristics of each.

3. **RBCs in Mammals**: In mammals such as rats, cats, and rabbits, the RBCs are anucleated, meaning they do not contain a nucleus. This is a common trait among mammals, as the absence of a nucleus allows for increased hemoglobin content and thus more efficient oxygen transport.

4. **RBCs in Amphibians**: In contrast, frogs are amphibians. Unlike mammals, frogs have nucleated RBCs. This means that their red blood cells contain a nucleus, which is a characteristic feature of many non-mammalian vertebrates.

5. **Conclusion**: Based on the analysis, the only species among the options provided that has nucleated RBCs is the frog. Therefore, the correct answer is **frog**.

### Final Answer:
Nucleated RBCs can be located in **frog**.